Recently, in the image pickup apparatus such as a small sized digital still camera, a video camera in which a small sized image pickup unit provided with a solid state image pickup element such as CCD (Charge Coupled Device) or CMOS (Complementary Metal-Oxide Semiconductor) type image sensor is mounted, the requirement for a zoom lens having the higher imaging performance is increased following to the high pixelation of the solid state image pickup element. Further, for the zoom lens of a small sized image pickup apparatus, the more size-reduction is required.
As a small sized zoom lens for a small sized image pickup apparatus, there is a zoom lens which is provided with a first lens group with a positive refractive power, a second lens group with a negative refractive power, a third lens group with a positive refractive power, and a fourth lens group with a positive refractive power, and in which the size-reduction in the thickness direction of the zoom lens is intended by being arranged a prism which bends the optical path in the first lens group (for example, refer to Patent Document 1).
(Patent Document 1) Tokkai No. 2000-131610
However, the conventional zoom lens as disclosed in Patent Document 1 has the longer entire length compared with the focal length thereof, and it is improper to use for the small sized image pickup apparatus.